Kidney Function: Tubular Reabsorption and Filtration. G28 - 1

The process by which large molecules, such as proteins, are taken back into the bloodstream from the renal tubules.

The filtration process in the kidneys allows substances to pass through the glomerulus based on size and not their chemical properties.

The amount of a substance reabsorbed by the tubules depends on its concentration in the blood.

A small change in glomerular filtration or tubular reabsorption can have a large effect on the amount of urine excreted.

Tubular reabsorption of substances can be independently controlled, allowing the body to finely tune the composition of urine.

The process of reabsorption involves the movement of substances across the tubular epithelial membrane, into the renal interstitial space, and then into the blood.

Substances can be transported across the renal tubular membrane using active or passive transport.

Reabsorption can occur through either the transcellular pathway (across the epithelial cells) or the paracellular pathway (between the cells).

The movement of fluids and solutes from the inside of blood vessels (capillaries) to the space between cells (interstitial space). It's driven by pressure differences and is a crucial step in the filtration process.

The movement of fluids and solutes from the space between cells (interstitial space) back into the bloodstream (capillaries). It's driven by osmotic pressure and pressure differences, helping to regulate fluid balance in the body.

The tight junctions between epithelial cells form a barrier, regulating the movement of substances between the tubular lumen and the interstitial space.

This type of transport moves solutes against their concentration gradient, requiring energy input. An example is the sodium-potassium pump.

This type of transport uses the energy from one molecule's movement down its concentration gradient to move another molecule against its gradient. It's often coupled with sodium.

A protein pump found in cell membranes that actively moves sodium out of the cell and potassium into the cell. It uses energy from ATP and is crucial for maintaining cell membrane potential and fluid balance.

The movement of molecules from an area of high concentration to an area of low concentration. It doesn't require energy.

The thin layer that surrounds capillaries, filtering substances entering and leaving the bloodstream.

A route that allows solutes to move through the cells of the nephron, crossing the apical membrane, cytoplasm, and basal membrane.

A route that allows solutes to move between the cells of the nephron, passing through tight junctions.

A type of active transport that uses energy from ATP to move molecules against their concentration gradient, from low to high concentration.

A protein embedded in the cell membrane that actively pumps sodium ions out of the cell and potassium ions into the cell, using energy from ATP.

The microscopic folds of the cell membrane that greatly increase the surface area for absorption in the proximal tubule.

A protein that facilitates the diffusion of a specific molecule across the cell membrane.

The net movement of sodium from the tubular lumen across the apical membrane into the cell, followed by its movement across the basal membrane into the interstitial fluid, and finally into the bloodstream.

When the movement of two substances is in opposite directions. One substance moving down its concentration gradient provides the energy for the other to move against its concentration gradient.

When the filtered load of a substance exceeds the capacity of the transport systems in the renal tubules.

The maximum rate at which a substance can be reabsorbed by the renal tubules.

The process where a substance is excreted in the urine because its filtered load exceeds the transport maximum, leading to saturation of the reabsorption systems.

A graph showing the relationship between the filtered load of a substance and its reabsorption by the renal tubules. It demonstrates how beyond a certain point (Tm), reabsorption plateaus, and excretion increases.

The process of removing waste products from the body, primarily through urine.

A protein that binds to both sodium ions and glucose or amino acids, facilitating their simultaneous transport across the membrane.

The movement of sodium ions down their concentration gradient, providing energy for the transport of glucose or amino acids against their concentration gradient.

The process by which glucose is reabsorbed from the tubular lumen back into the bloodstream.

A carrier protein located on the basal lateral side of the tubular cell that facilitates the movement of glucose out of the cell.

The process by which sodium ions are actively pumped out of the cell against their concentration gradient, using energy from ATP hydrolysis.

The difference in concentration and electrical charge between two areas, such as inside and outside a cell.

The energy required for the transport of molecules across a membrane is derived from the primary active transport of sodium.

The maximum rate of transport of a substance across the tubular membrane, beyond which further increases in the concentration of the substance in the tubular lumen do not increase the reabsorption rate.

The reabsorption of a substance is influenced by its concentration gradient between the tubular lumen and the interstitium. The higher the concentration in the lumen, the more reabsorption occurs. This is particularly relevant in the proximal tubule where junctions are looser.

In areas of the nephron with tighter junctions, such as the distal tubules, reabsorption mechanisms are primarily responsible for solute transport. This is because the leakiness of the junctions is reduced, and the concentration gradient alone is not enough to drive reabsorption.

The process by which water follows the movement of solutes from the tubular lumen into the interstitium. This creates a concentration difference that drives water movement across the tubular membrane.

The proximal tubule is highly permeable to water, allowing for rapid water reabsorption. This is because the osmotic forces driving water movement are strong, and the proximal tubule is designed to quickly reabsorb water.